patio on top of existing patio?

[DIYTastic]

Hi all

I'm hoping to have another attempt at my patio this summer.

My previous attempt was poor to say the least.

I used a "whacker plate" to compact the soil and the sand but obviously not enough because my patio slabs are now quite uneven.

Also, I totally forgot about a membrane and so have all sorts growing through the gaps

Anyway, although the patio is uneven, I believe it to be very solid. I laid it several years ago and so I don't expect any additional subsidence.

I'm thinking that I can lay my next patio ontop of the existing patio. This would save me the hassle of having to get in a whacker plate again.

I realise that this will mean the new patio is higher but this is fine as I don't mind a small step onto the grass (and it should help with puddles/water drainage).

Is this a stupid idea or a good shotcut?

Cheers


Wayne

 

[barryo]

It shouldn't be necessary to lift existing before laying new, providing you've still got a good height between the top of the new patio and the DPC. Should be minimum 150mm. To stop weeds you could lay a membrane on the old before laying the new? Remember to give a fall away from the house to prevent puddles.

 

[DIYTastic]

Thanks for that!

One more question. Would I need to put down a layer of sand ontop of the existing patio or should I just put the membrane down and then concrete/cement (never can remember the diff) the corners of the new patio slabs?

I'm assuming this is the correct method!

1. Cover existing patio with a layer of sand (to protect the membrand from sharp areas).
2. Lay membrane on sand.
3. Lay new slabs onto membrane with cement in corners
4. check/adjust slab level

Now, I immediately see a problem with this...what exactly is sucuring the new slabs to the ground! If anything, they'll be cemented to the membrane???

Yeah I know, a very silly question but I had to ask.

Cheers


Wayne

 

[barryo]

If you decide to use a membrane, don't worry 'cos the new patio isn't going to go anywhere once laid (unless it's at an agle of 45')! Actually I wouldn't bother with a membrane. And I wouldn't do dabs at each corner of the slabs. That encourages ant nests and weeds. If that's what you did with your original slabs, it's probably why they've moved. The ants burrowing causes voids = tilting.

I'd lay solid bed of a fairly dry mix 4:4:1 sharp sand/soft sand/cement. That won't go anywhere as long as you've set them right. I.E. don't tap the corners to level the slabs. Tap 1/2 way between the edge and centre. This avoids tilting.

See the best website available: http://www.pavingexpert.com/home.htm

Good luck.

 

[DIYTastic]

Hi Barryo

Thanks for the info.

Yep, I've seen that website before and BLOODY good it is too!

Was looking for advice about block paving for my driveway.

I thought it was the "norm" to lay slabs with the 4 wet corners so to speak...you learn something everyday!

The existing patio was laid onto a 1inch compact base of sharp sand mix (premixed patio sand you get from most major DIY stores).

I do remember tapping the corners though (which obviously hasn't helped much).

I'll give that website another look for patios and see what's what.

Again, thanks for the info/advice.

Cheers


Wayne